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Wednesday, June 19, 2013

What are the 3 instruments on SDO?

The Helioseismic and Magnetic Imager extends the capabilities of the SOHO/MDI instrument with continual full-disk coverage at higher spatial resolution and new vector magnetogram capabilities.

PI: Phil Scherrer, PI Institution: Stanford University.

HMI will use the acoustic waves and magnetic field measured at the surface of the Sun to study the motions of material inside the sun and the origins of the solar magnetic field.

We use the wave data to study the inside of the Sun. As the waves travel through the Sun they are influenced by conditions inside the Sun. The speed of sound increases where solar material is hotter, so the speed and angle at which the wave is generated determine how far it will penetrate into the solar interior. The shallower the angle, the shallower the penetration; the steeper the angle, the deeper the wave will travel. It takes about 2 hours for a sound wave to propagate through the Sun’s interior. The frequency and spatial pattern the waves make on the surface indicate where the waves have traveled. Scientists learn about the temperature, chemical makeup, pressure, density, and motions of material throughout the Sun by analyzing the detailed properties of these waves.

HMI will provide the first rapid-cadence measurements of the strength and direction of the solar magnetic field over the visible disk of the Sun. Scientists use this information to understand how the magnetic field is produced and, when combined with measurements from AIA, how that field produces flares and coronal mass ejections (CMEs), the storms of space weather.

AIA (Atmospheric Imaging Assembly)

The Atmospheric Imaging Assembly images the solar atmosphere in multiple wavelengths to link changes in the surface to interior changes. Data includes images of the Sun in 10 wavelengths every 10 seconds.

AIA is an array of four telescopes that will observe the surface and atmosphere of our star with big- screen clarity and unprecedented time resolution. It’s like an IMAX® camera for the Sun.
AIA will produce a high-definition image of the Sun in eight selected wavelengths out of the 10 available every 10 seconds. The 10 wavelength bands include nine ultraviolet and extreme ultraviolet bands and one visible-light band to reveal key aspects of solar activity. To accomplish this, AIA uses four telescopes, each of which can see details on the Sun as small as 725 km (450 mi) across— equivalent to looking at a human hair held 10 m (33 ft) away.

Because such fast cadences (number of images per minute) with multiple telescopes have never been attempted before by an orbiting solar observatory, the potential for discovery is significant. In particular, researchers hope to learn how storms get started near the Sun’s surface and how they propagate upward through the Sun’s atmosphere toward Earth and elsewhere in the solar system. Scientists will also use AIA data to help them understand how the Sun’s changing magnetic fields release the energy that heats the corona and creates solar flares.

Solar scientists will use the Extreme Ultraviolet Variability Experiment (EVE) to measure the sun’s brightness in the most variable and unpredictable part of the solar spectrum. The extreme ultraviolet, or EUV, ranges in wavelength from 0.1 to 105 nm.

EUV photons are much more energetic and dangerous than the ordinary ultraviolet rays that cause burns. If enough EUV rays were able to reach the ground, a day at the beach could be fatal. Fortunately, Earth’s upper atmosphere intercepts the Sun’s EUV emissions.

In fact, solar EUV photons are the dominant source of heating for Earth’s upper atmosphere. When the sun is active, EUV emissions can rise and fall by factors of hundreds to thousands in just a matter of seconds. These surges heat the upper atmosphere, puffing it up and increasing the drag on man-made spacecraft.